Coal for boiler fuel

ABSTRACT

To provide a coal for a boiler fuel ( 10 ) used as a fuel for a coal-fired boiler, the coal for a boiler fuel comprising a reformed coal ( 10 ) comprising a raw coal ( 2 ) and calcium ion-exchanged on a raw coal ( 2 ). The raw coal ( 2 ) comprises a lignite or a subbituminous coal, and the amount of calcium is an equimolar amount relative to the molar amount of sulfur contained in the raw coal ( 2 ).

TECHNICAL FIELD

The present invention relates to a coal for a boiler fuel, which is used for a fuel for a coal-fired boiler.

BACKGROUND ART

For a coal-fired boiler, which uses a coal as a fuel for combustion, because flue gas generated from the combustion of the coal contains sulfur oxide (SOx), the flue gas is discharged after sulfur oxide is removed from the flue gas.

For example, Patent Document 1 described below proposes the removal of sulfur oxide from flue gas as follows: super fine particles (1 to 100 nm) of calcium oxide (CaO) are generated by laser irradiation heating or plasma heating of a calcium compound such as calcium oxide (CaO), calcium carbonate (CaCO₃), or calcium hydroxide (Ca(OH)₂); the super fine particles are injected into the inside of a furnace or the inside of a flue to react with sulfur oxide in the flue gas, thus the sulfur oxide is removed from the flue gas.

CITATION LIST Patent Literature(s)

Patent Document 1: Japanese Unexamined Patent Application Publication No. H05-269341A

Patent Document 2: Japanese Unexamined Patent Application Publication No. H07-004610A

Patent Document 3: Japanese Unexamined Patent Application Publication No. H09-126411A

SUMMARY OF INVENTION Technical Problem

However, in the method proposed in the Patent Document 1, because it was necessary to install a laser ablation device, a high-frequency inductively coupled plasma generating device, an arc-plasma generating device and the like in the boiler device, the device cost became very high for a large-volume coal-fired boiler, and it was not practical.

Therefore, it is a strong demand to enable simple generation of super fine particles of calcium oxide at low cost.

Solution to Problem

The first invention to solve the problem described above is a coal for a boiler fuel used as a fuel for a coal-fired boiler. The coal for a boiler fuel comprises a reformed coal (ion-exchanged coal), the reformed coal comprising a raw coal and Ca ion-exchanged coal. The raw coal comprises a lignite or a subbituminous coal and the amount of calcium is not less than an equimolar amount relative to the molar amount of sulfur in the raw coal.

The second invention is the coal for a boiler fuel according to the first invention, in which the reformed coal further ion-exchanges iron. The amount ratio of iron is in a range from 0.1 to 5 wt % relative to dry-weight of the raw coal.

The third invention is the coal for a boiler fuel according to the first or the second invention, in which the reformed coal includes calcium ion exchanged on the raw coal in a range from 4 to 10 wt % relative to dry-weight of the raw coal, and the coal for a boiler fuel comprises a mixed coal which is a mixture of a basic coal comprising at least one kind from a bituminous coal, a subbituminous coal and a lignite and the reformed coal, and the amount ratio of the reformed coal is in a range from 10 to 50 wt %.

The fourth invention is the coal for a boiler fuel according to any of the inventions from the first to the third invention, in which the coal for a boiler fuel is subjected to pyrolysis treatment.

The fifth invention is the coal for a boiler fuel according to the fourth invention, in which the coal for a boiler fuel is further subjected to deactivation treatment.

Advantageous Effects of Invention

A coal for a boiler fuel pertaining to the present invention enables the presence of calcium oxide (CaO) as super fine particles (particle size: a few to a few tens of nanometers) from a calcium (Ca) portion ion-exchanged on the coal through combustion at high temperature, when the coal for a boiler fuel is injected and supplied to a boiler furnace as a fuel and subjected to the combustion at high temperature to become flue gas. Thus, the coal for a boiler fuel according to the present invention facilitates the generation of super fine particles of calcium oxide at low cost, and reduces the cost for the boiler device greatly.

BRIEF DESCRIPTION OF DRAWING(S)

FIG. 1 is a flow chart to illustrate manufacturing steps of the first embodiment of a coal for a boiler fuel pertaining to the present invention.

FIG. 2 is a schematic view of a treatment device for ion-exchanging treatment in FIG. 1.

FIG. 3 is a schematic view of a boiler device applied for the coal for a boiler fuel obtained from the manufacturing steps in FIG. 1.

FIG. 4 is a flow chart to illustrate manufacturing steps of the second embodiment of a coal for a boiler fuel pertaining to the present invention.

FIG. 5 is a schematic view of a boiler device applied for the coal for a boiler fuel obtained from the manufacturing steps in FIG. 4.

FIG. 6 is a flow chart to illustrate manufacturing steps of the third embodiment of a coal for a boiler fuel pertaining to the present invention.

FIG. 7 is a schematic view of a boiler device applied for the coal for a boiler fuel obtained from the manufacturing steps in FIG. 6.

FIG. 8 is a flow chart to illustrate a main portion of manufacturing steps of the fourth embodiment of a coal for a boiler fuel pertaining to the present invention.

FIG. 9 is a schematic view of a treatment device for ion-exchanging treatment in the other embodiments of the coal for a boiler fuel pertaining to the present invention.

DESCRIPTION OF EMBODIMENTS

Embodiments of the coal for a boiler fuel pertaining to the present invention will be described based on the drawings, but the present invention is not limited only to the following embodiments described based on the drawings.

First Embodiment

The first embodiment of the coal for a boiler fuel pertaining to the present invention will be described based on FIGS. 1 to 3.

A coal for a boiler fuel pertaining to the present embodiment is a coal for a boiler fuel used as a fuel for a coal-fired boiler. The coal for a boiler fuel comprises a reformed coal, which includes a raw coal comprising a lignite or a subbituminous coal, and calcium (Ca) ion-exchanged on the raw coal. The amount of calcium is not less than an equimolar amount relative to the molar amount of sulfur (S) in the raw coal.

The coal for a boiler fuel pertaining to the present embodiment can be obtained easily as illustrated in FIGS. 1 and 2 as follows: water 1, the raw coal 2 sulfur content 0.4 to 1.2 wt % (when dried)), the particle size (about 50 mm) of which is adjusted by pulverization (to the maximum particle size about 5 mm), and a calcium compound 3 such as calcium oxide (CaO), calcium carbonate (CaCO₃) or calcium hydroxide (Ca(OH)₂), are introduced into a treatment tank 111 of a treatment device 110 and stirred with a stirring blade 112 (pH 8 to 12). Calcium ion is eluted from the calcium compound 3 into the water 1 and contained in the water 1. By the contact with the raw coal 2, the calcium ion undergoes ion exchange with hydrogen ion of a hydroxy group (—OH) or a carboxyl group (—COOH) present on the raw coal 2. Thus, the calcium is ion-exchanged on the raw coal 2 at the amount described above (S11 in FIG. 1). This is followed by separation such as filtration from the interior of the treatment tank 111 to the exterior (S12 in FIG. 1), and water washing treatment as necessary (S13 in FIG. 1). This is further followed by filtration treatment (S14 in FIG. 1).

The coal for a boiler fuel (reformed coal) 10 manufactured as described above is subjected to drying and pulverization (particle size: about 0.1 mm), injected and supplied as a fuel into the inside of a boiler furnace 211 as illustrated in FIG. 3, and subjected to combustion at high temperature (temperature: 1500 to 1700° C.) to produce flue gas 6.

At this point, sulfur oxide (SOx) generated by the combustion at high temperature from sulfur (S) portion contained in the coal for a boiler fuel 10 exists in the flue gas 6. In addition, calcium oxide (CaO) generated from calcium (Ca) portion ion-exchanged on the coal for a boiler fuel 10 exists as the super fine particles (particle size: a few to a few tens of nanometers).

Then, sulfur oxide in the flue gas 6 can easily react with calcium oxide, which has a very large specific surface area due to being super fine particles, to produce calcium sulfate (CaSO₄).

The flue gas 6, sulfur oxide in which is converted to calcium sulfate, is cooled by heat exchange at a heat exchanger 212, and a solid content 7 containing the calcium sulfate and the like is removed by a particle removal device 213, followed by venting from a stack 214 to the exterior.

In other words, conventionally, the super fine particles (1 to 100 nm) of calcium oxide (CaO) are generated by laser irradiation heating or plasma heating of a calcium compound such as calcium oxide (CaO), calcium carbonate (CaCO₃) or calcium hydroxide (Ca(OH)₂), and the super fine particles are injected into the inside of the furnace or the inside of the flue to react with sulfur oxide (SOx) in the flue gas. Thus, the sulfur oxide in the flue gas is removed. In the present embodiment, calcium oxide (CaO) of super fine particles (a few to a few tens of nanometers) are generated in the flue gas 6 by combustion at high temperature using the coal for a boiler fuel (reformed coal) 10, in which calcium (Ca) is ion-exchanged on the raw coal 2 at the amount described above, as a fuel for the boiler furnace 211 and the super fine particles are reacted with sulfur oxide (SOx) in the flue gas 6. Thus, the sulfur oxide in the flue gas 6 is removed.

Therefore, conventionally, it is necessary to install a laser ablation device, a high-frequency inductively coupled plasma generating device, an arc-plasma generating device and the like in the boiler device. In the present embodiment, not only there is no need to install devices described above, but also there is no need to install a desulfurization device in the boiler device.

Therefore, according to the coal for a boiler fuel 10 pertaining to the present embodiment, it is possible to generate super fine particle (a few to a few tens of nanometers) of calcium oxide (CaO) easily at low cost and to reduce the cost of the boiler device greatly.

Meanwhile, it is necessary that the amount of calcium ion-exchanged on the raw coal 2 is not less than the equimolar amount relative to the molar amount of sulfur in the raw coal 2. This is because sulfur oxide generated by the combustion may not be removed sufficiently if the amount of calcium ion-exchanged on the raw coal 2 is less than the equimolar amount relative to the molar amount of sulfur in the raw coal 2.

Also, though a lignite or a sub-bituminous coal can be used as the raw coal 2, it is difficult to use a bituminous coal as the raw coal 2. This is because a lignite or a sub-bituminous coal has a hydroxy group (-OH), a carboxyl group (—COOH) and the like in the amount necessary to ion exchange with calcium ion and to ion-exchange calcium, but a bituminous coal does not have enough groups described above to ion-exchange calcium sufficiently.

Second Embodiment

The second embodiment of the coal for a boiler fuel pertaining to the present invention will be described based on FIGS. 4 and 5. Note that, for parts that are the same as the above embodiment, the same reference numerals as those used in the description of the above embodiment are used, and therefore duplicate descriptions of the above embodiment are omitted.

A coal for a boiler fuel pertaining to the present embodiment comprises the reformed coal, in which the raw coal 2 ion-exchanges calcium (Ca) in an amount not less than the equimolar amount relative to the molar amount of sulfur (S) in the raw coal 2 and, in addition, further ion-exchanges iron (Fe) in a range from 0.1 to 5 wt % relative to a dry-weight of the raw coal 2.

The coal for a boiler fuel pertaining to the present embodiment can be obtained easily as illustrated in FIG. 4 as follows: water 1, the raw coal 2, the calcium compound 3 and an iron compound 4 such as iron sulfate (FeSO₄) and the like are introduced into the treatment tank 111 of the treatment device 110 and stirred with the stirring blade 112 (pH 8 to 12), in the same manner as described in the embodiment above. While calcium ion is eluted from the calcium compound 3 into the water 1 and contained in the water 1, iron ion is eluted from the iron compound 4 into the water 1 and contained in the water 1. By the contact with the raw coal 2, the calcium ion and the iron ion undergo ion exchange with hydrogen ion of a hydroxy group (-OH) or a carboxyl group (—COOH) present on the raw coal 2. Thus, the calcium and the iron are ion-exchanged on the raw coal 2 at the amount described above, respectively (S11 in FIG. 4). This is followed by separation such as filtration from the interior of the treatment tank 111 to the exterior (S12 in FIG. 4), and water washing treatment optionally (S13 in FIG. 4). This is further followed by filtration treatment (S14 in FIG. 4).

The coal for a boiler fuel (reformed coal) 20 manufactured as described above is subjected to drying and pulverization (particle size: about 0.1 mm), injected and supplied as a fuel into the inside of the boiler furnace 211 as illustrated in FIG. 5, and subjected to combustion at high temperature (temperature: 1500 to 1700° C.) to produce flue gas 6.

At this point, in addition to sulfur oxide (SOx) and calcium oxide present in the flue gas 6 in the same manner as in the embodiment described above, iron oxide (FeO) generated from iron (Fe) portion ion-exchanged on the coal for a boiler fuel 20 exists as super fine particles (particle size: a few to a few tens of nanometers).

Then, sulfur oxide in the flue gas 6 reacts with calcium oxide to produce calcium sulfate (CaSO₄), as in the same manner as the embodiment described above. On the other hand, iron oxide in the flue gas 6, which has a very large specific surface area due to being super fine particles, contacts with carbon portion of the coal for a boiler fuel 20 with very high probability to complete combustion (oxidation) of the carbon portion by catalytic function.

The flue gas 6, in which sulfur oxide is converted to calcium sulfate while carbon portion is combusted (oxidized) thoroughly, is cooled by heat exchange at the heat exchanger 212. Then, a solid material 8 containing the calcium sulfate and the like and little unburned carbon portion is removed from flue gas 6 at the particle removal device 213 and the flue gas 6 is discharged from the stack 214 to the exterior.

In other words, in the present embodiment, iron oxide (FeO) of super fine particles (a few to a few tens of nanometers) in addition to calcium oxide (CaO) are generated in the flue gas 6 by combustion at high temperature using the boiler fuel (reformed coal) 20, in which not only calcium (Ca), but also iron (Fe) are ion-exchanged on the raw coal 2, as a fuel in the boiler furnace 211. Thereby, sulfur oxide is removed from the flue gas 6 as well as carbon portion is thoroughly combusted (oxidized).

Therefore, the present embodiment can improve the combustion efficiency inside the boiler furnace 211 compared with that of the embodiment described above.

Therefore, according to the coal for a boiler fuel 20 of the present embodiment, it is possible not only to gain the same effect as in the embodiment described above, but also to produce less unburned carbon portion remained in the solid material 8 that is collected in the particle removal device 213 than that of the embodiment described above.

Meanwhile, the amount of iron ion-exchanged on the raw coal 2 is preferably in a range from 0.1 to 5 wt % relative to the dry-weight of the raw coal 2. The reasons are following: If the amount of iron ion-exchanged on the raw coal 2 is less than 0.1 wt % relative to the dry-weight of the raw coal 2, the effect described above does not manifest itself sufficiently. If the amount of iron ion-exchanged on the raw coal 2 is more than 5 wt % relative to the dry-weight of the raw coal 2, it takes too much time to perform the ion-exchanging treatment, as well as the improvement of the combustion efficiency reaches the threshold.

Third Embodiment

The third embodiment of the coal for a boiler fuel pertaining to the present invention will be described based on FIGS. 6 and 7. Note that, for parts that are the same as the above embodiment, the same reference numerals as those used in the description of the above embodiment are used, and therefore duplicate descriptions of the above embodiment are omitted.

A coal for a boiler fuel pertaining to the present embodiment comprises a mixed coal of the reformed coal and a basic coal and the amount ratio of the reformed coal is in a range from 10 to 50 wt % in the mixed coal. In the reformed coal, the raw coal 2 ion-exchanges calcium (Ca) in an amount in a range from 4 to 10 wt % relative to the dry-weight of the raw coal 2 (not less than the equimolar amount relative to the molar amount of sulfur (S)), and, in addition, further ion-exchanges iron (Fe) in a range from 0.1 to 5 wt % relative to the dry-weight of the raw coal 2. The basic coal comprises at least one kind from a bituminous coal, a subbituminous coal and a lignite.

The coal for a boiler fuel pertaining to the present embodiment can be obtained easily as illustrated in FIG. 6 as follows: water 1, the raw coal 2, the calcium compound 3 and an iron compound 4 such as iron sulfate (FeSO₄) and the like are introduced into the treatment tank 111 of the treatment device 110 and stirred with the stirring blade 112 (pH 8 to 12), in the same manner as described in the embodiment above. While calcium ion is eluted from the calcium compound 3 into the water 1 and contained in the water 1, iron ion is eluted from the iron compound 4 into the water 1 and contained in the water 1. By the contact with the raw coal 2, the calcium ion and the iron ion undergo ion exchange with hydrogen ion of a hydroxy group (-OH) or a carboxyl group (—COOH) present on the raw coal 2. Thus, the calcium and the iron are ion-exchanged on the raw coal 2 at the amount described above, respectively (S11 in FIG. 6). This is followed by separation such as filtration from the interior of the treatment tank 111 to the exterior (S12 in FIG. 6), and water washing treatment optionally (S13 in FIG. 6). This is further followed by filtration treatment (S14 in FIG. 6). Then the reformed coal 30 is obtained. The coal for a boiler fuel pertaining to the present embodiment can be obtained easily by mixing treatment (S15 in FIG. 6) of a basic coal 5 comprising at least one kind from a bituminous coal, a subbituminous coal and a lignite, and the reformed coal 30, so that the amount ratio of the reformed coal 30 is in a range from 10 to 50 wt %.

The coal for a boiler fuel (mixed coal) 40 manufactured as described above is subjected to drying and pulverization (particle size: about 0.1 mm), then injected and supplied as a fuel into the inside of a boiler furnace 211 as illustrated in FIG. 7, and subjected to combustion at high temperature (temperature: 1500 to 1700° C.) to produce flue gas 6.

At this point, sulfur oxide (SOx) produced by the combustion at high temperature from sulfur (S) portion contained in the coal for a boiler fuel 40 exists in the flue gas 6. In addition, calcium oxide (CaO) generated from calcium (Ca) portion and iron oxide (FeO) generated from iron (Fe) portion ion-exchanged on the reformed coal 30 in the coal for a boiler fuel 40 exist as the super fine particles (particle size: a few to a few tens of nanometers).

Then, calcium oxide in the flue gas 6 reacts with sulfur oxide (SOx) generated from sulfur (S) portion contained in the reformed coal 30 and the basic coal 5 to produce calcium sulfate (CaSO₄). In addition, iron oxide in the flue gas 6 contacts with carbon portion in the reformed coal 30 and the basic coal 5 at high probability to combust (oxidize) the carbon portion thoroughly by the catalytic function.

The flue gas 6, in which sulfur oxide is converted to calcium sulfate while carbon portion is combusted (oxidized) thoroughly, is cooled by heat exchange at the heat exchanger 212 in the same manner as in the embodiment described above. Then, the solid material 8 is removed from flue gas 6 at the particle removal device 213 and the flue gas 6 is discharged from the stack 214 to exterior.

In other words, in the present embodiment, calcium in the molar amount not less than the sum of the molar amount of sulfur portion in the raw coal 2 and the molar amount of sulfur portion in the basic coal 5 is ion-exchanged on the raw coal 2. Thereby, sulfur oxide generated from the sulfur portion of the basic coal 5, which does not ion-exchange calcium, can be converted to calcium sulfate and removed from the flue gas 6.

Therefore, in the present embodiment, the basic coal 5, which does not ion-exchange calcium can be supplied as a fuel in the boiler furnace 211, and it is possible to reduce the usage amount of the reformed coal 30, which can be obtained by ion-exchanging treatment of calcium on the raw coal 2.

Therefore, according to the coal for a boiler fuel 40 of the present embodiment, it is possible not only to gain the same effect as in the embodiment described above, but also to produce the coal for a boiler fuel more efficiently than the embodiment described above and to reduce the cost of manufacturing.

Meanwhile, the ratio of the reformed coal 30 in the boiler fuel (mixed coal) 40 is preferably in a range from 10 to 50 wt %. In other words, the ratio of the basic coal 5 in the boiler fuel (mixed coal) 40 is preferably in a range from 50 to 90 wt %. The reasons are following: If the ratio of the basic coal 5 in the boiler fuel (mixed coal) 40 is less than 50 wt %, it is difficult to improve manufacturing efficiency of the coal for a boiler fuel 40 greatly. If the ratio of the basic coal 5 in the boiler fuel (mixed coal) 40 is more than 90 wt %, it may not be possible to convert sulfur oxide generated from the sulfur portion of the basic coal 5 to calcium sulfate sufficiently.

Meanwhile, the amount of calcium ion-exchanged on the raw coal 2 is preferably in a range from 4 to 10 wt % relative to the dry-weight of the raw coal 2. The reasons are following: If the amount of calcium ion-exchanged on the raw coal 2 is less than 4 wt % relative to the dry-weight of the raw coal 2, it may not be possible to convert sulfur oxide generated from the sulfur portion of the basic coal 5 to calcium sulfate sufficiently, depending on the characteristics of the basic coal 5 or the mix ratio with the basic coal 5. If the amount of calcium ion-exchanged on the raw coal 2 is more than 10 wt % relative to the dry-weight of the raw coal 2, it takes too much time to perform the ion-exchanging treatment (S11) on the raw coal 2, which brings about the reduction in manufacturing efficiency, and it may become difficult to reduce manufacturing cost.

Fourth Embodiment

The fourth embodiment of the coal for a boiler fuel pertaining to the present invention will be described based on FIG. 8. Note that, for parts that are the same as the above embodiment, the same reference numerals as those used in the description of the above embodiment are used, and therefore duplicate descriptions of the above embodiment are omitted.

The coal for a boiler fuel pertaining to the present embodiment is the mixed coal 40 subjected to pyrolysis treatment and, in addition, deactivation treatment.

The coal for a boiler fuel pertaining to the present embodiment is easily obtained as follows: As illustrated in FIG. 8, the mixed coal 40 obtained by the same manner as in the third embodiment described above is placed in the drying device then heated and dried (about 100° C.) and water component is removed (S21 in FIG. 8). This is followed by transfer to the inside of the pyrolysis device and heating and pyrolysis (about 400° C.) in inert gas atmosphere such as nitrogen gas is performed to remove volatile components including mercury (Hg) and the like (S22 in FIG. 8). This pyrolyzed coal is transferred to the inside of the cooling device to be cooled (about 50° C.) (S23 in FIG. 8), then transferred to the inside of the deactivation treatment device. Then the activated surface is subjected to deactivation treatment in the atmosphere for the deactivation (oxygen concentration: a few to 21 volume %) (S24 in FIG. 8), followed by shaping to a particulate shape in the briquetting device (S25 in FIG. 8).

In other words, the coal for a boiler fuel 50 pertaining to the present embodiment is obtained by subjecting the boiler fuel (mixed coal) 40 further to the pyrolysis treatment and, in addition, to the deactivation treatment.

Therefore, because most part of the volatile components such as mercury is removed beforehand for the coal for a boiler fuel 50 pertaining to the present embodiment, mercury content in the flue gas 6 can be greatly reduced and suppressed down to not more than the exhaust regulation concentration when the coal for a boiler fuel 50 is supplied and combusted as a fuel in the boiler furnace 211.

Therefore, not only that the same effects as in the case of the embodiments described above can be obtained, but also that the mercury content in the flue gas 6 can be greatly reduced for the coal for a boiler fuel 50 pertaining to the present embodiment. Thereby, there is no need to install a mercury removal device in the boiler device, and the cost for the boiler device can be further reduced.

Other Embodiments

Meanwhile, as the calcium compound 3, not only particles, particulate bodies and the like such as calcium oxide (CaO), calcium carbonate (CaCO₃), or calcium hydroxide (Ca(OH)₂) can be used, but also, waste materials containing calcium such as, for example, gypsum waste, cement waste, seashells, flyash, and iron and steel slag can be used.

Particularly, it is very preferable that calcium sulfate in the solid materials 7 or 8 collected at the particle removal device 213 is used as the calcium compound 3, because the source of calcium can be recycled and the generation of the waste can be greatly suppressed. Similarly, it is very preferable that iron sulfate in the solid materials 8 collected at the particle removal device 213 is used as the iron compound 4, because the source of iron can be recycled and the generation of the waste can be greatly suppressed.

When the waste materials described above are used as the calcium compound 3, it is very preferable to perform the following: As illustrated in FIG. 9, for example, while water 1 and the raw coal 2 are introduced into the treatment tank 111 of a treatment device 210 and stirred by a stirring blade 112, water 1 and the calcium compound 3 are introduced into the elution tank 213 and stirred by the stirring blade 214. Thereby, calcium ion is eluted from the calcium compound 3 and contained in the water 1 in the elution tank 213. While the water 1 is fed to the inside of the treatment tank 111 from the elution tank 213 through the filter 213 a, the same amount of water 1 fed into the inside of the treatment tank 111 is returned to the inside of the elution tank 213 from the treatment tank 111 through the filter 111 a. Thereby, calcium can be ion-exchanged on the raw coal 2 without the calcium compound 3 (waste material) coexisting with the raw coal 2 and the calcium compound 3 (waster material) and the raw coal 2 can be easily separated.

At this time, if calcium ion is not easily eluted from the calcium compound 3 (waste material) and water 1 does not easily exhibit pH 8 to 12, a pH adjusting agent (e.g. calcium hydroxide, calcium carbonate and the like) 9 can be added to the inside of the treatment tank 111 to adjust the pH of the water 1 to pH 8 to 12.

In the third and fourth embodiments described above, the mixed coal (the coal for a boiler fuel) 40 that is a mixture of the reformed coal 30, in which calcium and iron are ion-exchanged on the raw coal 2, and the basic coal 5, is explained. However, as the other embodiment, for example, the mixed coal (the coal for a boiler fuel) that is a mixture of the reformed coal, in which calcium is ion-exchanged, but iron is not ion-exchanged, on the raw coal 2, and the basic coal 5, can be used in the same manner as in the embodiments described above.

In the fourth embodiment described above, the coal for a boiler fuel 50 is manufactured as follows: The mixed coal (the coal for a boiler fuel) 40 is heated and dried in the drying device, and transferred to the inside of the pyrolysis device and heated and pyrolyzed; Then, the pyrolyzed coal is transferred to the inside of the cooling device and cooled, transferred to the inside of the deactivation treatment device and subjected to the deactivation treatment, then shaped to a particulate shape in the briquetting device. However, as the other embodiment, for example, the coal for a boiler fuel 50 can be manufactured as follows: The reformed coal 30 and the basic coal 5 are introduced into the drying device while mixing, and heated and dried, then transferred to the inside of the pyrolysis device and dried and pyrolyzed. Then, the pyrolyzed coal is transferred to the inside of the cooling device and cooled, transferred to the inside of the deactivation treatment device and subjected to the deactivation treatment, then shaped to the particulate shape in the briquetting device.

Also, in the fourth embodiment described above, it is described that the coal for a boiler fuel 50 is manufactured by subjecting the mixed coal (the coal for a boiler fuel) 40, which is a mixture of the reformed coal 30 and the basic coal 5, to the pyrolysis treatment and the deactivation treatment. However, as the other embodiment, it is possible to obtain the coal for a boiler fuel by subjecting the reformed coal 10 or 20, which is obtained in the first or the second embodiment described above, to the pyrolysis treatment and the deactivation treatment, for example.

Also, in the fourth embodiment described above, it is described that the coal for a boiler fuel 50 is manufactured by subjecting the coal for a boiler fuel 40 to pyrolysis treatment and deactivation treatment. However, as the other embodiment, it is possible to omit the deactivation treatment if the coal for a boiler fuel is used as a boiler fuel in a relatively short term after the pyrolysis treatment without long-distance transportation, for example.

As described above, the coal for a boiler fuel pertaining to the present invention can be realized, by combining the optional technical aspects described in the individual embodiments described above.

EXAMPLES

The following verification tests were performed to verify the effects of the coal for a boiler fuel pertaining to the present invention.

Preparation of Test Substances Test Substance A

A reformed coal (15 wt %), in which a raw coal comprising a lignite ion-exchanging calcium (8 wt %), and a basic coal (85 wt %) comprising a lignite were introduced in a dryer to be heated and dried while being mixed, then were transferred to the inside of a pyrolysis device to be heated and pyrolyzed. Subsequently, the pyrolyzed coal was transferred into the inside of a cooling device to be cooled, transferred into the inside of a deactivation treatment device to be subjected to deactivation treatment and shaped to a particulate shape in a briquetting device. Thus, the coal for a boiler fuel (Test substance A) was obtained.

Test Substance B

A reformed coal (15 wt %), in which a raw coal comprising a lignite ion-exchanging iron (2 wt %) as well as ion-exchanging calcium (6 wt %), and a basic coal (85 wt %) comprising a lignite were introduced in a dryer to be heated and dried while being mixed, then were transferred to the inside of a pyrolysis device to be heated and pyrolyzed. Subsequently, the pyrolyzed coal was transferred into the inside of a cooling device to be cooled, transferred into the inside of a deactivation treatment device to be subjected to deactivation treatment and shaped in a briquetting device to be a particulate shape. Thus, the coal for a boiler fuel (Test substance B) was obtained.

Comparative Substance

A basic coal (100 wt %) comprising a lignite was introduced in a dryer to be heated and dried while being mixed, then was transferred to the inside of a pyrolysis device to be heated and pyrolyzed. Subsequently, the pyrolyzed coal was transferred into the inside of a cooling device to be cooled, transferred into the inside of a deactivation treatment device to be subjected to deactivation treatment and shaped in a briquetting device to be a particulate shape. Thus, the coal for a boiler fuel (Comparative substance) was obtained.

Test Method

The test substances A and B described above and the comparative substance described above were each injected into the inside of a boiler furnace and combusted at high temperature as a fuel. The concentration of sulfur dioxide in the flue gas generated and the ratio of unburned carbon in the solid material collected were obtained separately.

Test Results

The test results are shown in Table 1 below.

TABLE 1 SO₂ concentration Ratio of unburned carbon (ppm) (wt %) Test substance A 90 2.3 Test substance B 95 0.5 Comparative 980 3.5 substance

As shown in Table 1 above, for the comparative substance (Ca and Fe were not ion-exchanged), the concentration of sulfur dioxide greatly exceeded the reference value (1,000 ppm) in the exhausted gas, and the ratio of unburned carbon in the solid material collected was relatively large.

In contrast, for the test substance A (ion-exchanging Ca only) and the test substance B (ion-exchanging both Ca and Fe), it was confirmed that the concentration of sulfur dioxide in the flue gas can be made less than the reference value (100 ppm). Furthermore, for the test substance B, it was confirmed that the ratio of unburned carbon in the solid material collected can be made very small.

INDUSTRIAL APPLICABILITY

A coal for a boiler fuel according to the present invention facilitates the generation of super fine particles of calcium oxide at low cost, and reduces the cost for the boiler device greatly. Therefore, it can be utilized very beneficially in the industry.

REFERENCE SIGNS LIST

-   1 Water -   2 Raw coal -   3 Calcium compound -   4 Iron compound -   5 Basic coal -   6 Waste gas -   7, 8 Solids -   9: pH-adjusting agent -   10, 20 Reformed coal (coal for a boiler fuel) -   30 Reformed coal -   40 Mixed coal (coal for a boiler fuel) -   50 Coal for a boiler fuel -   110, 120 Treatment device -   111 Treatment tank -   111 a Filter -   112 Stirring blade -   123 Elution tank -   123 a Filter -   124 Stirring blade -   211 Boiler furnace -   212 Heat exchanger -   213 Particle removal device -   214 Stack 

1. A coal for a boiler fuel used as a fuel for a coal-fired boiler, the coal for a boiler fuel comprising a reformed coal, the reformed coal comprising a raw coal and calcium ion-exchanged on the raw coal, the raw coal comprising a lignite or a sub-bituminous coal, and an amount of the calcium being not less than an equimolar amount relative to a molar amount of sulfur in the raw coal.
 2. The coal for a boiler fuel according to claim 1, wherein the reformed coal further ion-exchanges iron, and an amount ratio of the iron being in a range from 0.1 to 5 wt % relative to a dry-weight of the raw coal.
 3. The coal for a boiler fuel according to claim 1, wherein the reformed coal includes ion-exchanged calcium in a range from 4 to 10 wt % relative to a dry-weight of the raw coal, and the coal for a boiler fuel comprises a mixed coal, the mixed coal being a mixture of a basic coal and the reformed coal, the basic coal comprising at least one kind from a bituminous coal, a subbituminous coal and a lignite, and an amount ratio of the reformed coal is in a range from 10 to 50 wt %.
 4. The coal for a boiler fuel according to claim 1, wherein the coal for a boiler fuel is treated with pyrolysis treatment.
 5. The coal for a boiler fuel according to claim 4, wherein the coal for a boiler fuel is further treated with deactivation treatment. 